1. Field of the Invention
The present invention is generally related to phenanthroline compound and organic light emitting device using the compound. More specifically, the present invention related to phenanthroline compound having general formula (I) and formula (II), an organic light emitting device employing phenanthroline compound as electron transporting layer can lower driving voltage, prolong half-lifetime and increasing efficiency.
2. Description of the Prior Art
Organic light-emitting devices (OLEDs) have received much attention due to their potential applications to flat panel displays. OLEDs are generally composed of functionally divided organic multi-layers, e.g., hole transporting layer (HTL), emissive layer (EML), and electron transporting layer (ETL), and so on. A electron transporting material (ETM) have good charge carrier mobility and excellent operational durability can lower driving voltage and power consumption, increasing efficiency and half-lifetime of OLEDs. There are many kinds of ETM had been widely used for OLEDs, such as metal chelates (Alq3), benzimidazle, oxadiazole, Bipyridine-oxadiazole, triazes and phenanthrolines derivatives, and so on. Phenanthroline derivatives are well-know used for OLEDs such as bathophenanthroline (Bphen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP). But conventional phenanthroline derivatives exhibit lower Tg (Bphen=55° C., BCP=65° C.), lower heat-resistant (Td: weight loss <0.5% at 240° C. for Bphen and 260° C. for BCP. It's difficult to operate under deposition process and its OLEDs show lower stability and short half-lifetime.
Many works had modified phenanthroline chemical structure such as EP1097980A3 claim bathophenanthroline compound that introduce alkyl group and aryl group into 2,9-position of bathophenanthroline. US 2006/0097227 A1 claim phenanthroline compound that introduce fluorenyl group, fluoranthenyl group, perylenyl group into 2,9-position and 4,7-position of phenanthroline. But these electron-transporting materials (phenanthroline derivatives) are still needed corresponding to increase thermal stability and practical operation durability. Especially the half-lifetime and driving voltage needed to be improved for the purpose of industry practice.